A method for multi-connectivity between a plurality of base stations and user equipment includes estimating, at the user equipment, a first round trip time (RTT) taken in transmitting first data to a first base station, estimating, at the user equipment, a second RTT taken in transmitting second data to a second base station, and determining a size of the first data which is to be transmitted to the first base station, based on the first RTT and the second RTT.